Photographic silver halide transfer product and process



Dec. 28, 1954 E. H. LAND I l 2,698,237

PHoToGRAPHIc SILVER HALIDE TRANSFER PRODUCT AND PRocEss Filed Aug. is,1954 Supporlj (Pholosenslvc Silver Halde Emulsion Processing |4 Agnfl\\( l2 Supporl j I6 j (l2n Silver Precipilul'ng Layer FIG. I

/Prinl Receiving Elemn+ FIG. 2

Abrasion Resislanl CoolingL\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\lQ SilverPrecpihxlng Layer" FIG. 3

ATTORNEYS United States Patent@ 4PHOTOGRAPHIC"SENER1HALIDE TRANSFERPRODUCTv ANDl PROCESS vEdwin H. Land, Cambridge, Mass., assignertollolaroid Corporation, CambridgepMass., a corporation of DelawarerApplication August 16, Y'1954,' Serial No'. 449,995

31 Claims. (Cl: 95;@

Thisl'linvention relatesit'o photographic products and "processeslandprofe-particularly to Atransfer processes l,wherein -a latent imagein a silver halldeV emulsion is developed and whereina'vsoluble-Ysilver` complex obtained;byreaction with the'undevelopedsilver halide of said emulsion is transferred from` said emulsion andtheesilver thereof is precipitated in anotherwlayer to `for-ma positiveprint, and `tofproducts useful as printreceiving elements in saidprocesses.

This application is `a=contii'iuationin-part ofpmy. copendingapplication Serial 'Non 164,908, led May 29, 1950, for vPhotographicSilverHalide Transfer Product and Process, now abandoned, which, in.turn, is a continuation-in-part of my copendingapplication Serial No.727,385, ledFebruary 8, 1947 for Photographic Prodf uct and Process.l

One objectV of the present invention is to provide a transfer process ofthe foregoing type and products for i use' in -said processwherebyvthere are produced positive prints of good quality andystability from silver'halide emulsions of high speed.

Another object `of the present invention is to provide an improved'product particularly useful in the` foregoing i transfer processes asthe print-receiving element, sa1d product comprising a novel silverprecipitatinglayer adjacent one surface thereof,which layer serves to`eifect a'controlled precipitation of the silver from'the soluble ysilver complex and alsoacts to receive and suitably precipitating agentis suitably'supported;

Still another objectof the present invention is to provide a novelprint-receiving element which'also includes materials for greatly`improving tthe stability `of the y positive silver print formed in 'saidelement.

Other.objects'oftheinvention will in part be obvious and lwill in partappear hereinafter'.

` The invention accordingly comprises the kseveral steps and relationand orderof one or more of such steps with respectfto each of theothers,and theproductpossessing the' features, properties and the relation ofelements which are lexemplified in the following-detailed disclo-'sure'p'andthe scope of the` application of which will be indicated' inthe claims.

For a' fuller understanding of the nature and objects of the' invention,reference should` be had to the-following detailed description taken inconnection 'with'the accompanying drawings wherein:

Figure 1 is a diagrammatic enlarged sectional View illus'trating the'association of 'elements'during one v'stage 'ofthe performance of atransfer process and showing as ione of the elements an embodiment ofthenovelproduct`ofthe present invention, the thicknesses of. the variousmaterials being'exaggerated;

- Fig-2 is a perspective view, ywith parts broken away,

v, of one' form of print-receiving element upon which containers of theprocessingagent are so positioned as to be'capableof 'distributing theircontentssbetween the surface of the print-receiving. element and aphotosensi- .tive Aelement; and

y Fig. 3 is a viewflsimiiai te Figa of another form of theprint-:receiving element of the invention. The present inventioncomprehends improved processes rand products ofthe .type whereby apositive print is ob- 2,698,237 Patentedy Dec. 28, 1954 ICE tained in asingle step nby suitably treating .afsilver halide emulsion containing alatent. limage with. a uniformly applied layer of processingliqud. lPreferablygtheprocessing liquid is in a viscous condition and is spreadin a liquid iilm between the,.photosensitiveelementcomprising the silverhalidev emulsion and a print-receiving element comprising asuitablesilver precipitating layer. The liquid develops thelatent imagein theernulsion and forms a soluble silver complex, e. g.,.athiosulfateor a thiocyanate, with undevelolgaedsilver,halidejv This soluble silvercomplex is at leastvin rpart Ttransported. inthe direction ofthe.print-receiving.element andthe silver thereof islargely-precipitated,inthesilver precipitating layer of said element toform a positive image in silver.

It has been proposed to use in-,theformationof the silver transferprints by the foregoingnprocess certain compounds and elements` whose`presence during, the process has Va desirable-effect onsthetamountandcharacter of the silver precipitatedduring imageformation. For thispurpose,1such materials asnforexample, the metallic suldes andselenides,` rthioo'xalates, and .thioacetamides have been-disclosed inmy.U.'S. PatentNo. 2,647,056, issued July 28, .1953.' for.` One-StepPhotographic Transfer Process..H Other .precipitating 4agents havebeenproposed such, forexample, kas colloidal-silver.

VAccording to Athe present inventionpthe precipitation and aggregationof silver ,obtained byusing.silverf,pre cipitating agents, includinglthe above-mentioned fnaterials, is very ygreatly .improved'andkexpedited by' providing in the print-receiving elementas ladispersingtmedium or matrix for said agents a layer formed primarily ofparticles of silica. Ther particles are Vsmall enough so that when laiddown as a thin layer they present acontinuous surface tothe naked eyeMrather than a skeletal or porous structure'. To', this end the particlesaresubmacroscopic in size, i. e., small enough to beindistinguishable asdiscrete or separate particles bythe' naked eye. Preferably they are sosmall as `to yapproach `or be of colloidal size but are neverthelessdiscrete particles rather than integral parts of asingle continuouscoalesced mass. Thus, the matrix of thejpresent invention is formed ofdefinite particles which are'essentiallylsilica and which aresufliciently smallv to be indistinguishable as vparticles by the nakedeye'- when formed, into a layer andwhose minimum average 'sizeiswof'colloidaly rather than of molecular proportions.'4 The essentiallyipure forms of silica such as the silica laero'gel available' under thetrade vname "Santoc'el C2 or the solid contentof the hydrated silicadispersione available under the trade 'names Ludox and Syton give bestresults. However, it is possible to use highly pulverized-formsof the-les'sl pure silic'as such, for example, as those/obtained frornnaturalsources, provided,` however,l thatl these materials fhave a high silica:content of approximately 70% orgreater by weight and the'particlesthereof are submacroscopic in size.v Exampleslofsuch materials arethesilicas derived from diatornites variouslykn'own as diatomaceous earth.kieselgnhr'andV infusorial earth. Also useful, when pulverized toparticles small enough in size,'is powdered glass. However, the`preferred materials aresilicas whose solid con tent comprises'of theorderof 97% ormore of SiOz.

`The ynovel silver precipitating layer including the' silica and thesilver precipitating agent lis preferably applied to a suitable'support,forfexamplesby beingcoated on .thesupport ingthe form of a suspensionwhich contains a substantiallyngreaterwamountpfl'the silica thanof the`precipitating' agent." The supportfmay'be `formed'fof a non-siliceous`material Vsucll'tasi'paper,"regenerated cellulose;polyvinylalcohol,'cellulose ethers such as methyl cellulose,"rethyl;cellulose, or their.derivatives, such as sodium carboxymethylgcellulose and: hydroxyethyl cellulose,'and other natural and-'syntheticgums and resins whi'ch willfform continuouslms`and which are rela-`tively'fstable, mechanically, inrthepresence of water and lalkaliL--These supportingsheets 1 are opaquewhen a relection print is desired`andtransparent.when a transparency is desired.

4Suitable assilverprecipitatingagents,arethe metallic `sulfides andselenides, these Hterms. being understood to include' theselenosulidesthe polyr'sultides',N and thei-poly- Vselen'ides.',Preferredin' .this I. groupware. kthe vso-called heavy metal sulfides,e. g., of zinc, chromium, gallium, iron, cadmium, cobalt, nickel, lead,antimony, bismuth, silver, cerium, arsenic, copper; and the heavy metalselenides, e. g., of lead, zinc, antimony and nickel. For best resultsit is preferred to employ the sulfides whose solubility products in anaqueous medium at approximately C. vary between 10-23 and 1030 andspecifically the salts of zinc, cadmium and lead. Also suitable asprecipitating agents are heavy metals such as silver, gold, platinum,palladium and mercury, and in this category the noble metals arepreferred and are preferably provided in the matrix as colloidalparticles. Also useful as silver precipitating agents are the salts ofthese heavy metals, preferably the simple inorganic and readilyreducible salts such as silver nitrate, gold chloride and gold nitrate.In some instances, the metals are introduced into the matrix as saltsand then reduced in situ prior to the use of the reception material inthe silver transfer process to give a layer whose silver precipitatingagent is the colloidal metal. Where the salts are relatively lightorheat-sensitive, this reduction may be accomplished simply by exposingthe silver precipitating layer to diffuse light or to heat. Still othersatisfactory silver precipitating agents are certain of the thiocompounds, e. g., dithiooxamate and its lead and zinc complexes,potassium dithiooxalate and the lead and nickel complexes thereof andthioacetamide. The silver precipitating agents as noted above areprovided in a highly dispersed condition, preferably as colloidalparticles.

In general, the sulfides and selenides of the alkali metals and alkaliearth metals such as sodium, potassium, cesium, calcium, barium andmagnesium are too soluble to give optimum pictorial quality, althoughthe provision of a silica layer as a vehicle for such precipitatingagents greatly improves the results obtained with said agents.

The concentration of the silica in the silver precipitating layer ispreferably high enough to give a macroscopically continuous discretestratum thereof on the surface of the print-receiving element whenapplied thereto and the silver precipitating agent is present in a verysmall amount.

It has been determined that further improvements in image quality areobtained when using one or more of the heavy metal sulfides andselenides as silver precipitating agents if the sulfide or selenide ionsof the crystals are prevented from wandering or diffusing duringprecipitation from their original loci in the precipitating layer. Inthe following discussion of this and other phenomena involving theaction of the sulfide and selenide salts, reference will be made to thesulfides alone, but it is to be understood that wherever such referenceis made, the same, unless otherwise stated, is generally applicable tothe selenides.

To prevent the diffusion and wandering of the sulfide ions, there ispreferably included in the silver precipitating layer or closelyadjacent thereto at least one metallic salt which is substantially moresoluble in the processing agent than the heavy metal sulfide used as thesilver precipitating agent and which is irreducible in the processingagent, said more soluble salt having, as its cation, a metal whose ionsform sulfides which are difficultly soluble in the processing agent andwhich give up their sulfide ions to silver by displacement. Accordingly,when such sulfied ions are present, the metal ions of the more solublesalt have the effect of immediately precipitating the sulfied ions fromsolution.

The special function of this combination of a sulfide, a more solublemetallic salt and a silica will be better understood by considering thenew sequence of reactions which takes place when a print-receivingelement so constituted is used in a silver halide transfer processinvolving a silver halide developer and a silver halide solvent, such assodium thiosulfate. This sequence of reactions is perhaps best describedin my article One-Step Photography appearing in Section A of theJanuary, 1950 issue .of the Photographic Journal (British) as follows:

Firstz The silver ion in the silver halide of the negative is protectedby its environment in the crystalline halide from being reduced, but itprefers the thiosulphate ion as an associate, so the silver halidedissolves.

Second: The silver ion is now protected from reduction by thethiosulphate complex, but it prefers the sulphide ion as an associate,so that silver sulphide is formed and would be precipitated as such ifit were not .f0.1` 'Che fact that the sulphide ionin spite of theinsolubility of the crystalline compound-does not protect the silver ionfrom reduction. Thus, the silver ion has been safely pried loose andtransported to a new site where it becomes silver, and the transportingions are free to carry on their cyclic efforts. Is this then the end?Actually, it is the beginning, for while we have learned how to extractthe silver ions from the negative and to precipitate them as reducedsilver rapidly, we are just beginning to consider how to build up anacceptable positive from the point of view of appearance (and of coursewe have not yet considered our problems of stabilizing an image residentin this complicated reagent).

What we nd when we use sulphide ions to release silver ions from thethiosulphate complex is the following gamut of problems:

(1) Sulphide ions in solution provide so many points of initiation thatan enormous number of grains start growing. If these become large thewhole picture will be too dense. If they remain small, the picture willbe bright yellow (you will recall that the colour of silver' colloidsdepends on the particle size).

(2) There is a tendency for the grains in the shadows, opposite theunexposed portions of the negative, where much silver is available, togrow larger than the grains in the medium tones, where the availablesilver concentration is low, producing an unpleasant combination of blueshadows and yellow high lights.

(3) Some of the sulphide ions migrate into the negative, dropping theconcentration in the positive and fogging the negative.

Thus, having determined how to extract silver ions from the appropriatepart of the negative, and how to reduce them to silver atoms, we arestill confronted with the problem of how to build these atoms intoarrays of the correct diameter for absorbing visible light. We must alsoachieve adequate constancy in diameter so that high light and shadow arethe same hue.

Since the sulphide ions are the last factor in the chain of eventsleading to silver precipitation, let us corisider how these might bearranged to inuence the array of silver atoms. Let us suppose that wecan arrange the sulphide ions in clusters, allowing the diameter of thecluster to be that of the mass of silver we seek to build. The actualmass of sulphide ions might then be very low indeed-subject to one vitalproviso, namely that as the sulphide ions perform their cyclic function,they are retained within the diameter that we have chosen for thecluster. If we can meet this condition, then we can cause the silveratoms to fill in the volume of the cluster to make our mass of silver ofthe required density and size. To do all this we must extend the chainof circumstances that we have been following from the negative outward.

By forming colloidal crystals of heavy metal sulphides which are notreducible generally in or soluble in the developer, and by aggregatingthese colloidal crystals into galaxies of our chosen diameter, we canarrange the sulphide ions as we desire them. In this new environment thesulphide ion is bound in place until the silver thiosulphate complextouches it. The silver ion-just as it once left the halide ion for thecomplexnow leaves the complex ion to form the sulphide. The sulphidesimilarly leaves the metal ion for association with the silver. Then thesilver is reduced-but mark you, reduced in situ-reduced at the pointwhere we originally deposited the colloidal particle of metal sulphide.We have started well in building up our mass of silver. But the sulphideion, now free, is not likely to encounter the metal ion to which it wasbound if it escapes from the galaxy and wanders off. We are in danger ofreverting to some extent to the problems that occurred with the solublesulphide. This danger can be avoided by intro ducing into the positivesheet at the time of manufacture a relatively high concentration of asoluble salt of the same metal that we used in the colloidal sulphide(or indeed of some other metal, providing that its sulphide is moresoluble than silver sulphide and is not reducible in, or soluble in, thedeveloper). After the viscous developer is spread, the metal salt in thepositive sheet dissolves, and because of the relatively highconcentration of these metal ions, the sulphide that is freed at itsoriginal site by the reduction of the silver is at once captured beforeit can leave that site, and reprecipitated as the sulphide of the metal.In this way, the diameter of the Mft-9,698,237

f galaxyf-isf-maintainedyinspitewof the-cyclic use of thesulphide-ions'f.- vThe-silver ions-1am reduced-to-silver overmetal-sulphide galaxies.

One remarkable aspect of picturesmade in this way fis thatthe-silver'inthef positive has-,very high coveringV-power-in'the-order-of tive -times thatfrof the silver in l `thenegative.*Consequently a good Apositive-canbe made from a layerofsilverhalidethatis many times thinner f.

of positive, it is impressive to see how thin -a `layer of negativematerial suflicest-The negative image, when i such4 a ,thin emulsion is'used, is only just visibleyet the positive derived'fromthesamefa'mou'ntf of'silver'is rich "."Land brilliant. t L" type'ofintensification: Furthermore, v*since onlythe sur- 1 Thus, we see thatthis process provides a .L .face of the'negative" isf-involved, there isgainin speed,

`Indeed the migration" distance for ,the silver ions goingfrom'thenegativesheet -to-thepositive imagecanbe extremelysmall'; vWehave seen'that'these ions'co'me from very nearthe'surfaceofthe-negative, and 'we c'an,1if we f vchoose,-.prec'ipitate*thefsilver in`the viscouspositive layer r aidstheformation-fof'the-aforementionedgalaxies, and

" the dithionates.

f miumynickeland-lead are preferred.

- .'fatl the surfaceof-the-Lnegative,-Thus,the combination of minimizedvlight'scatteri'ng vinthe-negative, the short mi- .s'gration' distancefor theV silver ions, and rthe-prompt pre- -cipitationA of-th'em :whenthey `"rea'ch'tthepositive,- results f in ka processiWithfquite'goodmesolving' power. -Further- Y. more, the-pictures are` byall-ordinary standards ygrainless,

Vthe-same area that-We-chcsetor the-original. galaxy, and the, rdiameter.ofN the fmassof silveris such thatfounimage Aisfthe'colour@we-predetermined when we prepared the .l

- than lis` ordinarily-*required for aqnegative. V-`While fullthickness-negatives can be usedffonmaking this new kind .form the 'suldeinthesilverpreeipitatingflayer thatthere isy substantially noexcess of`the more solubleelmetallic saltsffm saidlayer and toprovide themore-soluble ionrfeap'turingsalts in another-layer over or Iunder the..silver precipitatinglayer.

lt will be :readily appreciated that the performance of aphotographicprocessing, which involves the-formation zor" aflpositiveprint by means-of a single liquid applicaltion;.withoutrecourse-tobaths'of liquid, is toibe greatly desired-Where this can be accomplishedto give -a positive print of good pictorial quality from emulsionsofhigh speed-as caribe had by following the practicesdescribedE:l'iereinabove:4 `However, because theusual developing solution is `ahighlyl alkaline solution containing a develcoping; agent-which-zrapidlyoxidizes in an alkaline envronment;y 1t will `also-be appreciated that4'undernormal we'fcircumstance's this type fof-'liquid processingvprovides in -the print-receivingelement a material which, upon exposureto air, tends to-formundesirable stains. ,-Unless the print issnbiected'- toa thorough washing, this condition will normallyadverselyr alectwith time the` quality "of an image vformed in'aprint-receiving layen.y .How-

I' ever,O afs pointed out in my U. S.- Patents ,No1 2,584,030,

issueddanuary 29 1952, No; 2,635,048, issued April 14, y1953, andNo.'2,64-4,756, issuedl July ,7, Y1953,.it;is possible to avoid thisstain by includingin the print-receiv- 'because ofthe way in wliiclrthesilver isideposited and aggregated?v- (Underlined words added ormodiiied.)

- The silver"precipitatingr agent is'dispersed in silica which it isevident, from theforeg'oing, thatthe presence of the' more soluble salt,whichprovides thecations for -1 e' capturing.' they fr'eesuldeiions, hasthe-effect of -malntainingthis desirable'aggregationf-of thesulfide ionsdurzing i-the-"silver'l precipitationn-These more soluble or ron- Acapturing salts may be the soluble salts of any of the following metals:cadmium, cerium(ous),f cobaldgus),

atlsiro'nf'lead,nickel,"manganese,` thorium and tin.` factoryfsoluble'a1d"stable" salts 'of the' above metals may be found, for'example,amongthe"following.groups of salts: the"aceta't`es,the nitrates, theborates,`the chlorides, theisulfates, thev hydroxides, theformates, 'thefcitrates and Theac'etates and nitratesof zinc, cadalso preferable'touse the :white orlightly colored salts I although for "certainspecialfpurposes the more darkly colored salts can be employed.

Y i -One method of` providing the print-'receiving' element f j witha'jsilver 'precipitating-layer Icoiitairllngithe'silver prel'clipitatingagenn the salts fo'rscapturmgl the 'sulfide ions In general,it is ing layera substance Which- `substantially ,eliminates thestain-formingpropensltyof the developing solution in the y yrint-receivin yla er. 30A D g Y lIt-istto 'bev observed that thefion-capturing-salts, to

" -which'freference has been madefhereinabove',umay also "serveth'efunction of improving-the stability of the positive4 yprin'r` providedthat they possess, in addition to the f Vaforementioned characteristics,the requisitesspeeied in my `above-mentionediU. S. 'Patent No.A2,584,030. For

i example,- ifY the ion-capturing salt is a-salt of-a rnetal'whichslowly forms insolublefor slightly soluble metallic hydroxides' with thehydroxyl ions/in the alkaline processing liquid, it Vwill suitablycontrol the alkalinity of the print- -receiving element .tosubstantially, if not totally, prevent i they formation ofundesirabledeveloperr stains.

The-stabilizing saltshould noty be a fogging agent and l preferablyshould be White or lightly colored and should tions.

give hydroxides which are 'also whiteA or light in color.

llt'-shrmld-not decompose Vin aqueous non-alkaline solu- For thispurpose, the acetates and-nitrates,1 especially--of^lead, zinc; nickeland cadmium, are preferred.

Of the salts hereinabove set out as being satisfactory forpreventing-the sulfide ions from wandering, allexcept the hydroxide will'function satisfactorily as stabilizing-agents.

Inl addition,-the soluble salts, -for example, of=alurninum` maybe-mediostabilize although they will not'serve to 2 trap ythe wandering sulfideions.

Theuse of the novel products ofthepresent invention in theiperformanceof a silver-halide transfer process is illustrateddiagrammaticallyinFig. l, wherein 10 repandthe silica-is to form-an aqueous d ispersion ofsilica aerogelto which there'is 'addeda-'smtable quantity of v oneor'more'of theiori-capturing saltsra'lihereafter a substantiallyless'erlmolar `quantity of' a Asoluble sulfide,

such assodium sulde, is'added.'l The-'anions 'of sulde r andlthecations'offthetioncapturing"salt combinefto precipitate from "thesolution relatively insoluble crystals of the's'ulfide'lof the *metal of-theion-capturing salt, thereby'eonverting `a portion" ofk thelatter`to`the'lsullide'. This produces "afdispersion of the-insolublesuldeinfthe silica solt while'leaving in solution th'e remainder of theloncapturing saltsx" The' concentrationi of theflatter 1n the vini-tiall solutionu in relation to the added amountcf the soluble suldeis such asto give lin the final layer' a sub- A 4:st'antiallygreater-amount of the'ion-eapturing `salt 1n pro- 'portion to thesulde.n U

ln another" method of forming Vthesilverpreclpltatmg vlayerfthesol'of`silicavisiirs't applied as acoatingy to the print-'receiving elementand7 isl thereafter impregnated with one'ormore'of the ion-capturingg salts1by'immersing said coated-surface of the element 1n a-solut1on ofsaid' salts and permitting the same to dryl-v Thereafter,

l' by dippihg'thefsheet in `asoluble sulfide va predetermined i portion'vofy the fmoresoluble salblin-the silica layer is 'fconvertedto give-theinsoluble sulde. ySome-ofthe ion- *'jcapturing saltV is alsodissolvedout' of the layer-'during the Y"second immersion so that allowance forthis loss is i rnadein ftheduantity of theV soluble salt'which'isappliedin the firstimmersione-HR. may also befdesirableto 'so -resentsaphotosensitiveelement comprising-a support 10a and= a A-photosensitive,silver halide emulsion layer 10b, lift-representsa layer of relativelyviscousprocessing agent, and -12 -is one-embodiment of the-novelprintreceiving element of the invention upon which a transfer print-isobtained-fby the-process. As shown, the printreceiving element 12comprises a suitableA support 12a and al silver precipitating layer 16.

- lLiquid layer 14 may be obtained byspreading the processing-agent,Vfor example, in a manner disclosed in my above-mentioned-U S. Patent No.2,647,056, and the t processing agent may be oneofthe lm-formingprocessnthey may be in partfor wholly added to thejprocessing 0U' liquid as itis spread betweenelementst-l@ and -12, said 4reagents beingso located onor kadjacent the surface of onefor both of'- said elements asto bedissolvedY by or H otherwise interacted with the-*liquidy agent When-thelatter "wets said-surface. 1

lTheliquidproeessing-agent may be providedforspreading as a layer 14between elements 10 and 12 by being contained in an elongated rupturablecontainer 20 which, as shown in Fig. 2, has a length at least equal tothe transverse dimension of the area of photosensitive elcment 10 towhich the liquid processing agent is to be applied. One or morecontainers 20 may be attached to one of elements 10 and 12 and, in Fig.2, two such containers are shown secured to the print-receiving surfaceof element 12, being spaced apart, lengthwise of said element, adistance equal at least to the length of a single frame of thephotosensitive element 10. Said elements 10 and 12 may be connectedtogether so that they can be superposed with the container so positionedthat it can release its contents in a film therebetween. The container20 is preferably inexpensive and disposable and so constructed as to becapable of retaining the liquid processing agent or composition thereinfor relatively long periods of time without vapor loss or oxidation. Oneexample of a suitable container of this type is formed from a singlemultilayer sheet of material comprising three laminae. The inner lamina,which provides the inner surface of the container, is formed of amaterial which is chemically inert to the reagents in the processingagent and which is impervious to the liquid of the agent. One class ofmaterials suitable for this purpose, particularly where the processingagent is an alkaline solution, is the polyvinyl acetals, and of theacetals, polyvinyl butyral is a preferred species. A compositioncomprising 60% to 72% by weight of polyvinyl butyral, 10% to 23% byweight of nitrocellulose, and approximately by weight of dibutylsebacate is satisfactory as the inner lamina. The intermediate lamina ispreferably impervious to the vapor of the processing agent and isformed, for example, of a metallic foil such as lead or silver foil. Theouter or backing lamina is formed of a strong, deformable, relativelyinexpensive sheet material such as a kraft paper.

The container 20 is preferably formed by taking the single sheet ofthree-ply material and folding the same medially at 22, and thereaftersecuring the end marginal portions 24 and the longitudinal portions 26of the two folded faces to one another, providing a central space orcavity 28 for containing the processing liquid.

To fill the container it is possible to adhere together the oppositelongitudinally extending marginal portions 26 and one of the endmarginal portions 24, the container being filled through the other endwhich is thereafter sealed.

Photosensitive element may be any of the cornmercially availablephotosensitive silver halide films, the term films being understood toinclude paper-backed emulsions. The products of the present inventionare particularly useful in improving the results obtained when thetransfer process is carried out with one of the highspeed photosensitivesilver halide emulsions such as the emulsion of the relativelyhigh-speed orthochromatic films, e. g., Eastman Kodak Verichrome film,having an ASA speed rating of 0200 and an ASA exposure index rating inthe daylight of 50, and the extremely high-speed panchromatic emulsions,e. g., Eastman Kodak Super XX Pan having an ASA speed rating of 0400 andan ASA exposure index rating in the daylight of 100, and Ansco Triple SPan.

Element 12 may be formed by applying to a suitable support 12a, forexample, of baryta paper, a coating of a suspension or sol of the silicacontaining the silver precipitating agent. This sol is permitted to dryand provides layer 16. The suspension of silica may be obtained bydispersing the silica, for example, in water, and then adding the silverprecipitating agent either` directly or by introducing into the solsalts whose reaction product is the precipitating agent. The sol mayalso be applied to the sheet without the silver precipitating agent, andthe sheet with the layer of silica thereon may then be dipped in asolution or mixture of the silver precipitating agent to deposit thelatter in said layer.

When the foregoing liquid composition is spread or otherwise provided ina layer 14 between elements 10 and 12, the liquid thereof permeates thephotosensitive layer 10b and the developing agent acts to develop thelatent image in said layer. Almost simultaneously with the development,the complex-forming substance, i. e., sodium thiosulfate, forms asoluble silver complex with the undeveloped silver halide, and thesilver complex is transported by the liquid of the processing agent tolayer 16 of element 12. The presence of layer 16 results in a vigorousand relatively concentrated precipitation of the silver from the silvercomplex to form an image of improved density and color, and having moredesirable f gamma and contrast characteristics than would be obtained inthe absence of the silica.

Examples of processes for forming a positive image wherein a silverhalide transfer takes place and examples of the novel product of theinvention which is used as the print-receiving element in theperformance of said processes are given below, but it is expresslyunderstood that these examples are merely illustrative and that theinvention is not limited to the materials or proportions set outtherein.

The processing agent is prepared by dissolving the sodium carboxymethylcellulose, for example the commercially available Hercules 1362 mediumviscosity type, in the water in a mixer at room temperature, and thesolution is mixed therein for approximately one hour. Thereafter, thesodium sullite, sodium hydroxide, sodium thiosulfate and citric acid areadded to the solution, the addition being effected in an inertatmosphere, for example of nitrogen. Upon dissolution of thesematerials, the hydroquinone is added and the solution is further mixedfor an hour at approximately room temperature in a nonoxidizingatmosphere of nitrogen.

A print-receiving element 12 provided with a silver precipitatingstratum 16 is prepared by having at least the baryta-coated surfaceportion of a strip of baryta paper immersed in a mixture comprising thefollowing ingredients:

1% solution of sodium sulfide cc-- 280 Silica aerogel grams 30 Solutioncontaining 30 g. cadium acetate, l g. neutral lead acetate and 30 g.zinc nitrate dissolved in 100 cc. of water cc 92 to provide a thincoating of these materials on said surface. As the baryta paper isremoved from the bath, the excess mixture on said surface is removedfrom the sheet as, for example, by the action of a soft buffer roll 0nsaid sheet as it leaves the bath.

The processing agent is spread in a layer 14 of approximately .C02-.003in thickness between the coated surface of element 12 and thephotosensitive silver halide emulsion 10b of a photosensitive film 10.Emulsion 10b is a relatively high-speed orthoehromatic emulsion like theemulsion of Eastman Kodak Verichrome film, and has been exposed topredetermined subject matter to form therein a latent image of saidsubject matter, support 10a for said emulsion being a white paper. Thelaminations formed by the spreading of the processing agent in a layer14 between elements 10 and 12 is kept intact for approximtaely one-halfto one and one-half minutes, preferably one minute, and at the end ofthis time element 12 is stripped from element 10. Element 12, when sostripped, carries a positive print in silver of the subject matter ofthe latent image in emulsion 10b. The sodium carboxymethyl cellulose oflayer 14 adheres to coating 16 of element 12 and solidifies to form afilm thereon. The print obtained in this manner has good color, densityand other pictorial qualities.

Other materials may be substituted for those used in the foregoingprocess and the proportions may be varied to an appreciable extent. Forexample, the film-forming material in the processing agent which impartsthe desired viscosity to the latter may be any of the high molecularweight polymers which are stable to alkalis and which are soluble inaqueous alkaline solutions. For example, such other plastics ashydroxyethyl cellulose, polyvinyl alcohol and the sodium salts ofpolymethacrylic acid and polyacrylic acid may be used. The plastic ispreferably contained in the agent in sufiicient quantities to .impart tothe composition a viscosity in excess of 1,000 centipoises at aftemperaturez'of approximatelyiteff 24 C.v Preferably,V the viscosityoflthe processingfagene-V is ofthe orderof 1,000 to 200,000'centipoisesr'f2 Otherdeveloping agents rfi-.ty be used, vfor example one el:

of the following: p-aminophenolhydrochloride; bromohydroquinone; iehlorohydroquinone; vdiami-nophenol; hy# drochloride; diaminophenoldihydrochlorid'e;toluliydri quinone; monomethyl-paininophenol sulfatej'afl mixture consisting 'oy Weight of one-half hydroquinonefand one-Hhalf p-'hydroxyphenylaminoacetic-y acid;` 'land =a=iimixturef S10-consisting by weight of onefourth-hydroquinone vand .1 :if

three-.fourths p-hydroxyphenylaminoacetic acid.V i t To form. thesoluble silver complex,such otherlcom-x-w plex-forming substances aslsodiumithiocyanate,i-ammow nium thiocyanate and ammonia `may be.employedel l Examples of further iembedirnentsofi the' novelpririt-Fvreceiving elements of the present invention 'and theprocfiw' esses forforming the same are given below:`

ExampleZ 20 Example 3- The process of forming thesheet described' inExample.`

therein a mixture of the following materials which gives a coating ofsilica containing palladlum sulde:...

Example 5 The process of forming thesheet-described in Example 2 maybeperformed by substitutingfor the mixturey therein a mixture of thefollowingm aterials which gives a coating of silica containing cadmlumsulfide:

96 cc. of a 20% solution of cadmium acetate:v i g. .of silica aerogel 30cc. of a l% solution of sodiumsulide"` Example. 6 The process of formingtheV sheet 'described in Example 2 may be performed bysubstitutingformthe mixture therein a mixture of the following materialswhich gives a coating of silica containing'zinc sulfide::-"`

cc. of a 37.5% solution of zinc nitrate 7.5 g. of silica aerogel v vcc..of a 1% solution of sodium sulfide Example -7 The process of`forming thesheet describedin Example 2 may be performed by substituting"for-'themixture therein a Vmixture ofthe following .materials-whichgivesfi` a coating of silica 'containing magnesiumtsulde'zi:

48 cc. 'of a 40% solutionof magnesium acetate.. 7.5 g. of silicaaerogely 18 cc. of a 1% solution of sodiurn'suliideV Example 8 Theprocess of forming the sheet'described inEimniple` Cfr 2 mayibeperformedby"substitutng`-for thejmixture"'-` therein a mixture of thefollowing'materials which 'givesi a coating `of silica containing leadselenide:

96 cc. cfa 40%-neutral lead acetatesolution 15 g. .of/silica aerogel 30cc..of..a 1%i sodiumselenide` solution ma 85 aerogel in 100 cc. ofwater.

A a film 10 at; the completion ofthe processingi-the film formingVnmaterialLremains attached to the. photosensitive 'Y 10 Example 9T TolSSgramsOfLudox, asolutio'n.,eor1tainingapproxi: mately.,30% 'ofhydratedcolloidal sili ca..in` water\,.there is added .9.0 .gramsofwater....Thereafter 24 cc.4 of 4a solut tion formed by adding 3.grams ofsodium sulfide Ato 46icc. of water 4is added: 'no .thissuspension,.followedby'. the is...

additionoflZ ccfofa solutionformed .bydissolving 2.6; grams'of leadacetate-in 20 cc`.`of Water. .1

,The resulting mixture isrubbedfby hand onthe-.surface s of theprint-receiving support. Itis preferable t'o..wipe off any, excess ofthe mixture fronithe. paper .afterthe rubbingopera'tion'.

To obtain different precipitating. agentsin ,the silver. precipitatinglayerthat is formed accordingI to .theprocess of Example. 9, there maybesubstituted forithe 2.6: grams.-... of lead acetate one of the followingsalts in the fllowing quantities:

Gramsw Zinc facetate 1.42 Cupricjfacetate S 1.34 l'.Manganous acetate'1.60

Cadmiumacetate 1.92

Example 1.0i

A suspension is formed by mixing 420 grams of silica This sol orsuspension is then rubbed: ionto-` the baryta-coated i surface of af'sheet of baryta'paper; xThe sheetis then dried and dippedy ina 3%waterisolutionl of sodium sulfide forthirty seconds. The excess liquid.issqueegeed from the-sheetfas -it is re- -1 movedx-fromf the solution.-L 2 may be performed by substituting for the mixture Example. :1 1

-A suspension'isftforrned'by `mixingf20 grams"of-silicalit I aerogel infcc.'\of=water..1lThis s`o1-or suspensionfis' then rubbed onto thebaryta-coated surfaceff'of VAa-shee`t=0f- A baryta paper. The sheet is:thendried and dipped in a 3% Water solution of sodium sulfide forthirty seconds. The excesslliquidis sq'ueegeedr-froinftheY sheetaskvitis `rey movedzifrom the solution. '*The sheety is `then againdriedll and dipped for ten seconds in =a second solution'which fis c a5%1 water solution of neutral lead-acetate. "The 'excessliquidzissqueegeedfrom the surface'of -the sheethand the' sheetyistdried onceftmorebefore being` used.

ExcessV moisture is removed from the sheet as it leaves theN ).3olut1on,'for example with a glass rod, .and.the..sheetlis..

ried.

For the baryta paper of any of the foregoing examples;

, there may be substituted a filmof plastic such, for exampleiexaspolyvinyl-alcohol,v hydroxyethylv 'cellulosef' i sodium carboxymethylcellulose, regenerated cellulose or f other .self-supporting sheetlikematerials upon which the.....\.: novel vg'silverprecipitatinglayer oftheV present invention may berdeposited.

In anotherform of theproduct of the present invention,

.it mayz'be desirable to provide acoating onthe silvergw..k

precipitatinglayer '1'6" of 'a material, such as a plastic, moreabrasionLresistantzthan the silicaof the precipitating layer in order toprotectisaid layer. Thisovercoat' of ai plastic materialtmay also serveas a layer whichprevents'" the adhesionto. the element 1-2wof thefilm-forming'rnaL i l' terial Iof lthe-llayertof processing'liquid 14'so fthatwhenf said element 12 is stripped away from the photosensitive18 which may be, for example, gum arabic, cellulose acetate-hydrogenphthalate, polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose,ethyl cellulose, cellulose nitrate, sodium alginate, pectin andpolymethacrylic acid. Layer 18 preferably has a thickness of the orderof 1-3 microns, although if it is relatively water permeable itsthickness may be appreciably greater. Layer 18 may contain one or moreof the neutralizing agents which tend to improve the stability of thefinished print.

To provide any of the print-receiving elements 12 of Examples 1 throughl2 with a protective coating 18 of a more abrasion-resistant plasticwhich may also serve as a layer for minimizing the adhesion between thefilm-forming material of layer 14, particularly where said material issodium carboxymethyl cellulose, said elements 12 of each of saidexamples may be processed as follows:

Example 13 The processed sheet has roll coated thereon against a smoothsurface such, for example, as the polished surface of a metal drum, aaqueous solution of polyvinyl alcohol in a layer whose thickness is ofthe order of ,001 inch. An equivalent amount by Weight of hydroxyethylcellulose or polymethacrylic acid may be substituted for the polyvinylalcohol of this example.

Example I4 The processed sheet is dipped into a 2% solution of celluloseacetate, the cellulose acetate being dissolved in a mixture of methanol,ethyl acetate and methyl cellosolve, the proportions of said solventsbeing in the ratio of 1:3:3 by volume, respectively. The dipped barytapaper is removed from the solution in a vertical position to permit theexcess liquid to drip olf, a sullicicut quantity of the solutionremaining on the surface of the paper to provide the latter with acoating of cellulose acetate of the desired thickness.

Example 15 A 10% solution of cellulose acetate-hydrogen phthalate inacetone is roll coated on the processed sheet in a thickness ofapproximately .001 inch.

In a similar manner, such other materials as methyl cellulose, cellulosenitrate, sodium alginate, ethyl cellulose, gum arabic and pectin may beapplied as layer 18 to the processed sheet. It is, of course, understoodthat suitable solvents for the materials are employed, said solventsbeing preferably water for such materials as are readily water soluble,and may be toluene for ethyl cellulose and a mixture of methanol andethyl acetate for cellulose nitrate.

Although the silver precipitating layer of the present invention isconstituted primarily of the silica, it may contain therein a smallquantity, preferably not exceeding 10% by weight of the silica, of afilm-forming substance such as gum arabic, hydroxyethyl cellulose or anyof the other materials heretofore mentioned as being suitable for theabrasion-resistant coating 18 on layer 16. The addition of this smallquantity of plastic facilitates application of the layer 16 onto thesupport therefor. An example of one way of forming a layer 16 containinga small quantity of film-forming material is the following:

Example 16 The following ingredients are mixed in the order named:

A sheet of baryta is dipped in the mixture, withdrawn, and the excessliquid squeegeed therefrom.

Other plastics may be substituted for the gum arabic. Also, bysubstituting salts of other metals for the cadmium vrltetate differentmetallic selenides may be obtained in e so Another class of compoundsespecially useful in controlling the alkalinity of the print-receivingelement after the formation of the positive print therein is the organiccompounds which react in alkaline solution to consume alkali, asdisclosed in my above-noted U. S. Patent No. 2,635,048. Preferred fromthis class are the esters (including lactones), the anhydrides, thealphaahalohydrins and the aldehydes which have a specific rate ofalkaline hydrolysis at C. greater than 80 liters per mol per minute and,from this class, the preferred species are compounds which do notvolatilze too rapidly, i. e., cornpounds whose boiling points are inexcess of 150 C.

Examples of preferred species of these compounds are: diethyl oxalate,ethyl oxamate, diethyl d-tartrate, a hydroxybenzaldehyde, dimethyldiacetyltartrate, dimethyl fumarate, dimethyl malate, dimethyl oxalate,dimethyl tartrate, polyethylene oxalate, benzoic anhydride, di-nbutyloxalate, n-butyl oxamate, di-n-butyl tartrate, trismethyl citrate, ethylcyanoacetate, ethyl N-B hydroxyethyl oxamate, glucono delta lactone,glyceryl trimethyl oxalate and cellulose methyl oxalate,di-B-hydroxyethyl malonate, hydroxyethyl lactate, diethyl malate,diethyl tartrate, di-B-hydroxyethyl malate, ethyl acetoacetate, dibutylmalate, butyl lactate, diethyl malonate, glyceryl chlorohydrin, anddi-B-hydroxyethyl succinate.

The positive print is subject to several sources of instability whichstem, for example, from the oxidation Y of the developer in thehighlights, the discoloration of some of the unexhausted chemicalcomponents in the positive prints by exposure to visible and nearvisible radiation, and the partial bleaching of the silver.

It has been determined that these effects are most nearly eliminated bycombining the stabilizing effects of the soluble metallic salts and theorganic alkali-consuming compounds, i. e., by using at least one of eachof these classes of stabilizers in the print-receiving element.

Examples of suitable print-receiving elements which embody thiscombination of stabilizers, together with the novel silver precipitatinglayer of the invention, are the following:

Example 17 The baryta-coated surface of a sheet of baryta paper isimmersed in a mixture consisting of:

Water cc-- 1000 Arabol -cc 150 Dimethyl d-tartrate grams-- 400 Leadacetate do 70 Cadmium acetate do 50 Zinc acetate do 40 The sheet is thendried and there is applied over the The baryta-coated surface of a sheetof baryta paper is dipped in a solution consisting of:

Ethanol cc-- 1000 Zinc nitrate grams 120 Ethyl oxamate do The treatedsurface of this sheet is then provided with a sulfide-containing coatingconsisting of the following:

Silica aerogel grams-- 300 1% aqueous solution sodium sulde cc-- 2800Cadmium acetate grams..- 30 Lead acetate do l Zinc nitrate do 30 Watercc-- It is to be noted from the foregoing examples that the silverprecipitating agent is present in the sheet in a very small amount.Concentrations, for example, as low as 2x10*6 to 2 l0"5 gram-moles foreach square foot of the surface area of the print-receiving element haveproven adequate.

Since certain changes may be made in the above product and processwithout departing from the scope of the invention herein involved, it isintended that all matter contained in the above description or shown inthe accompanying drawing shall be interpreted as illustrative and not ina limiting sense.

What is claimed is:

l. A photographic product comprising a photosensitive material whichincludes a silver halide layer, a base layer having adjacent one surfacethereof a silver precipitating stratum, said stratum comprising a silverprecipitating agent dispersediamong colloidal:particles-.ofv silica, anda rupturable containing means holding a1 liquid,-

said product having positioned thereiniphotographic reagents, includinga sliver haiide developer and asilver halide-51 solvent, said containingmeans and said layers .Y

being so held together that saidcontaining means is capable, uponrupture, of releasingat least a :part ofy receive a depthwise diffusionof said solution fromlsaid its contents tol permeate superposedyportions'iof said y silverighalide layer and said base layer,saidiliquid, upon withthe undeveloped silver halide of said silverhalide layer, said liquid, upon release, additionally transport ing saidsoluble silver complex infthe direction of said silver precipitatingagent wherein part at leastof the 1 soluble silvencomplex is reduced tosilvei.to produce the positive print. v

2. A photographic product comprising a silver halide layer, abase layerand -a rupturable container holding 'a liquid, said layers and saidcontainer being attached together so as to permit said layers -to besuperposed with said container so positioned as to release its .liquidfor spreading in a film between said layers, the liquid in saidcontainer comprising a silver halide developer, a silver halide solventand a thickening agent, said lbase layer having adjacent one surfacethereof a stratum includinga silverprecipitating agent dispersed amongcolloidalA particles of silica.

3. A photographic product capable of forming transfer printsl inconjunction with a photosensitive'silver halide element, said productcomprising a rupturable containing means, holding a liquid, and a sheetsupport upon which said containing means is mounted, said sheet supportproviding an image-receiving area adjacent said containing means ontowhich said liquid is spreadable in a thin layer directly from saidcontaining means, saidproduct carrying a silver halide developer and asilver halide solvent, said sheet support having,- adjacent the surfacemounting said containingv means and at least coextensive with saidimage-receiving arb a silver precipitating stratum Acomprising a silverprecipitating agent dispersed among colloidal particles of silica, saidsilver halide developer, said silver halide solvent and said liquidbeing suiicient in amount and being so located, in relation to saidimage-receiving l area that the spreading of said liquid over said-areadisperses silver halide developer and silver halidesolvent throughoutsaid area in adequate quantity to form a transfer print of a latentimage in an area of a contiguous silverfhalide element equivalent tosaid image-receiving area. 'Y

4. A ph-otographic product capable of forming transfer printsin`conjunction with a photosens'itive silver-"halide element-, saidproduct comprising a rupturable containing means, holding an alkalineliquid solution of aA silver halide developer, a silver halide solventand a film-forming plastic, and a sheet support upon whichsaid'containing means is mounted, said sheet support providing animage-receiving area adjacent said containing means lori-to whichl saidliquid solution is spreadable in a thin layer directly from saidcontaining means, said support having a silver precipitating stratum atleast coextensive in area with said image-receiving area, said silverprecipitating stratum comprising a silver precipitating agent dispersedamong colloidal particles of silica, said solution and the silverprecipitating agent in said stratum being suliicient jf in amountso thatthe spreading of said liquid over said image-receiving area providesafdispersion of silver halide developer-and silver halide solvent inadequate quantity to form a transfer print of a latent image in an areaof Aa contiguous `silver halide element equivalent to saidimage-receiving area.

5. The process of forming Vpositive images in silver which comprisesdeveloping a latent negative image in a silver halide emulsion layerwith a solution comprising a silver halide developer and a silver halidesolvent to form an--imagewise distribution of soluble silver complex insaid emulsion layer, transferring from said emulsion layerby-limbibition at least part of said imagewise dis-V tribution of saidsoluble silver complex toran image-carryf ing layer comprising a supportand an image receiving stratum so superposed adjacent said emulsionlayeras to emulsion layeiwithout appreciably disturbing. the image- Wise`distribution of the silver complex in. said solution, said stratumcomprising a distinct and separately applied coating of colloidal silicaon said support and including/ff a silver precipitating agent dispersedin said coating,fandl reducing to silver the silver lions of saidsolublesilver com# l plex in said stratum to forni an image insilver`amongA colloidal particles of saidsilica which is a positiveofthe subject matter of said latent image.

6. A print-receiving element for having transfery prints I Y formedthereon by precipitating the silver -of an image-V wise distribution ofa soluble silver complex brought intocontact therewith, said elementcomprising a support and a silver precipitating layer, at least onesurface portion off. v

said element, including said layer, being permeable to an aqueoussolution of a soluble silver complex, said layer comprising a silverprecipitating agent linely dispersed' among colloidal particles ofsilica, said support for the silver precipitating layer comprising asheet 'of' baryta paper, said silver precipitating agent being atleast'one substance from the class consisting of heavy metals, metalsuliides and selenides, and organic thio compounds.

7. A print-receiving element for having transfer-prints formed thereonby precipitating the silverof an-image-f wise distribution of a solublesilver complex brought-into f contact therewith, said element comprisinga support and a silver precipitating layer, at least one surface portionof said element, including said layer, being permeable yto an aqueoussolution of a solubleisilver complex, said layer being a distinct andseparately applied coating on said support and comprising a silverdispersed among colloidal particles of silica, said silver precipitatingagent being at least one substance from the class consisting of heavymetals, metal -suliides and selenides, and organic thio compounds andbeing present in a concentration of the order of 2 10*5 gram-moles foreach square fo-ot of the surface area of said layer.

.8. A photographic product comprising a photosensitive material whichincludes a silver halide layer, a basel layer having adjacent onesurface thereof a silver precipitating stratum, said stratum comprisinga matrix of subrnacroscopic discrete particles of silica and a silverprecipitating agent dispersed in said matrix, and a ruptur-l ablecontaining means holding a liquid, said product-havv ing positionedtherein photographic reagents, including'a lsilver halide developer anda silver halide solvent, said containing means and said layers being soheld together v that s aid containing means is capable, upon rupture,of'

releasing `at. least a part of its con-tents to 'permeate superL posedportions of said silver halide layer and saidl base i layer, saidliquid, upon release, rendering said silverhalide developer and saidsilver halide solvent effective todevelop a latent image in said silverhalide layer and to form soluble silver complex with the undevelopedsilver halide of said silver halide layer, said liquid, upon re-- lease,additionally transporting said soluble silver come" plex in thedirection of said silver precipitating agen-t wherein part at least ofthe soluble silver complex is reduced to silver to produce the positiveprint.

9. A photographic product comprising a silver halide layer, a base layerand a rupturable container holding a liquid, said layers and saidcontainer vbeing attached together so as to permit said layers to besuperposed with said container so positioned as to release its liquidfor spreading in a film between said layers, the liquid in saidcontainer comprising a silver halide developer, a silver i halidesolvent and a thickening agent, said base layer com# prising anon-siliceous support and having adjacent one surface thereof a stratumincluding a silver precipitating agent dispersed among submacroscopicparticles ofV silica which on lthe average are not smaller thancolloidalin size.

10. A photographic product capable of forming transfer prints inconjunction with a ph-otosensitive silver halide element, said productcomprising a rupturable containing means holding a liquid, and a sheetsupport upon which said containing means is mounted, said sheet supportproviding an image-receiving area adjacent said containing means ontowhich said liquid is spreadable in'a y thin layer directly from saidcontaining means, said produ' uct carrying a *silver halidedeveloper anda'silverfh-aldef solvent, said sheet support having, adjacent thesurface l' precipitating agent finely mounting said containing means andat least coextensive with said image-receiving area, a silverprec1p1tating stratum comprising a matrix of submacroscopic discreteparticles of silica and a silver precipitating agent dispersed in saidmatrix, said silver halide developer, said silver halide solvent andsaid liquid being sucient in amount and being so located, in relation tosaid imagereceiving area, that the spreading of said liquid over saidarea disperses silver halide developer and silver halide solventthroughout said area in adequate quantity t-o form a transfer print of alatent image in an area of a contlguous silver halide element equivalentto said image-receiving area.

11. A photographic product capable of forming transfer prints inconjunction with a photosensitive silver halide element, said productcomprising a rupturable containing means holding an alkaline liquidsolution of a silver halide developer, a silver halide solvent and afilm-forming plastic, and a sheet support upon which said containingmeans is mounted, said sheet support providing an imagereceiving area4adjacent said containing means onto which said liquid solution isspreadable in a thin layer directly from said containing means, saidsupport having a silver precipitating stratum at least coextensive inarea with said image-receiving area coated on a non-siliceous sheet,said silver precipitating stratum comprising a silver precipitatingagent dispersed among submacroscopic particles of silica which on theaverage are not smaller than colloidal in size, said solution and thesilver precipitating agent in said stratum being sullcient in amount sothat the spreading of said liquid over said image-receiving areaprovides a dispersion of silver halide developer and silver halidesolvent in adequate quantity to form a transfer print of a latent imagein an area of a contiguous silver halide element equivalent to saidimage-receiving area.

l2. The process of forming positive images in silver which comprisesdeveloping a latent negative image in a silver halide layer, reacting asilver halide solvent wi-th part at least of the undeveloped silverhalide of said layer to form `an imagewise distribution of solublesilver complex in said layer, transferring in solution at least part ofsaid imagewise distribution of said soluble silver complex to animage-receiving material comprising a support and a distinct andseparately applied coating of submacroscopic, discrete particles ofsilica on said support and so located in relation to said silver halidelayer as to receive the solution of said complex without appreciablydisturb- Ving its imagewise distribution, said coating having -a silverprecipitating agent dispersed among said silica particles, and reducingto silver the silver ions of said soluble silver complex at saidimage-receiving material to form an image yin silver.

13. The process of claim 12 wherein said support is a flexible sheetsupport.

14. The process of claim 13 wherein said sheet support `is paper.

15. The process of claim 13 wherein said sheet support is a sheet oftransparent plastic.

16. The process of claim 12 wherein said silver precipitating agent isfrom the class consisting of heavy metals, metal sulfides and selenides,and organic thio compounds.

17. The process of forming positive images in silver which comprisesdeveloping a latent negative image in a silver halide emulsion layerwith a solution comprising a silver halide developer and a silver halidesolvent to form an im-agewise distribution of soluble silver complex insaid emulsion layer, transferring from said emulsion layer by imbibitionat least part of said imagewise dis- F tribution of said soluble silvercomplex to an image-carrying element comprising a support and a distinctand separately applied coating of submacroscopic particles of silica a-tleast colloidal in size and so superposed adjacent said emulsion layeras to receive a depthwise diffusion of said solution from said emulsionlayer without appreciably disturbing the imagewise distribution of thesilver complex in said solution, said coating having a silverprecipitating agent dispersed among said particles of silica, andreducing to silver the silver ions of said soluble silver complex insaid coating to form an image in silver among said particles of silica.

18. The process of claim 17 wherein said particles of silic-a form amacroscopically continuous matrix for said (iii precipitating agent andsaid matrix is a coating on a flexible sheet support.

19. The process of claim 18 wherein said sheet support is a sheet ofpaper.

20. The process of claim 18 wherein the sheet support is a sheet oftransparent plastic.

21. The process of claim 17 wherein said silver precipitating agent isfrom the class consisting of heavy metals, metal suliides and selenides,and organic thio compounds.

22. The process of claim 17 wherein said silver precipitating agent is acolloidal heavy metal.

23. The process of claim 17 wherein said silver precipitating agent is acolloidal noble metal.

24. The process of claim 17 wherein said silver precipitating agen-t isat least one compound from the class consisting of the heavy metalsuldes and selenides.

25. The process of claim 17 wherein said silver precipitating agent isan organic thio compound.

26. A print-receiving element for having transfer prints formed thereon.by precipitating the silver of a soluble silver complex brought intocontact therewith, said element comprising a support and a substantiallynonphot-osensitive silver precipitating layer provided as a discretemacroscopically continuous, distinct and separately applied coating onone surface of said support, one surface portion of said elementincluding said layer being permeable to an aqueous solution of a solublesilver complex, said layer having a major proportion by weight ofsubmacroscopic particles of silica on the average at least colloidal in`size and having finely dispersed therethrough a minor proportion byweight of particles of a silver precipitating agent for aiding thereduction and precipitation of metallic silver from silver complex ionsin the presence of a reducing agent, said silver precipitating agentbeing from the class consisting of heavy metals, metal suldes andselenides, and organic thio compounds.

27. A print-receiving element for having transfer prints formed thereonby precipitating the silver of a soluble silver complex brought intocontact therewith, said element comprising a support and a substantiallynon-photosensitive silver precipitating layer provided as a discretemacroscopically continuous, distinct and separately applied coating onone surface of said support, one surface portion of said elementincluding said layer being permeable to an aqueous solution of a solublesilver complex, said layer having a major proportion by weight ofcolloidal particles of substantially pure silica and having finelydispersed therethrough la substantially lesser amount by weight ofparticles of a silver precipitating agent for aiding the reduction andprecipitation of metallic silver from silver complex ions in thepresence of a reducing agent, said silver precipitating agent being fromthe class consisting of heavy metals, metal suliides and selenides, andorganic thio compounds.

28. A print-receiving element for having transfer prints formed thereonby precipitating the silver of a soluble silver complex .brought intocontact therewith, said element comprising a non-siliceous support and asubstantially non-photosensitive vsilver precipitating layer provided asa discrete macroscopically continuous, distinct and separately appliedcoating on one surface of said support, one surface portion of saidelement including said layer being permeable to an aqueous solution of asoluble silver complex, said layer having a major proportion by weightof submacroscopic particles of silica aerogel and having finelydispersed therethrough a substantially lesser amount by weight ofparticles of a silver precipirating agent for aiding the reduction andprecipitation of metallic silver from silver complex ions in thepresence of a reducing agent, said silver precipitating agent being fromthe class consisting of heavy metals, metal suldes and selenides, andorganic thio compounds.

29. The product of claim 26 wherein said silver precipitating agent is acolloidal heavy metal.

30. The product of claim 26 wherein the silver precipitating agent is acompound from the class consisting of the heavy metal sulfides andselenides.

31. The product of claim 26 wherein said silver precipitating agent isan organic thio compound.

(References on following page) References Cited in the le of this patentUNITED STATES PATENTS Number Number Name Date 2,296,636 Hanahan Sept.22, 1942 5 59365 2,352,014 Rott June 20, 1944 2,626,867 Webster Jan. 27,1953 18 FOREIGN PATENTS Country Date Great Britain Oct. 15, 1931 FranceMar. 23, 1942 Netherlands May 16, 1947 OTHER REFERENCES Burmistrov,Phofographic Journal, vol. 60, August 10 1936, pp. 452-459.

1. A PHOTOGRAPHIC PRODUCT COMPRISING A PHOTOSENSITIVE MATERIAL WHICHINCLUDES A SILVER HALIDE LAYER, A BASE LAYER, HAVING ADJACENT ONESURFACE THEREOF A SILVER PRECIPITATING STRATUM, SAID STRATUM COMPRISINGA SILVER PRECIPITATING AGENT DISPERSED AMOUNG COLLOIDAL PARTICLES OFSILICA, AND A REPTURABLE CONTAINING MEANS HOLDING A LIQUID, SAID PRODUCTHAVING POSITIONED THREIN PHOTOGRAPHIC REAGENTS, INCLUDING A SILVERHALIDE DEVELOPER AND A SILVER HALIDE SOLVENT, SAID CONTAINING MEANS ANDSAID LAYERS BEING SO HELD TOGETHER THAT SAID CONTAINING MEANS ISCAPABLE, UPON RUPTURE, OF RELEASING AT LEAST A PART OF ITS CONTENTS TOPERMEATE SUPERPOSES PORTIONS OF SAID SILVER HALIDE LAYER AND SAID BASELAYER, SAID LIQUID, UPON RELEASE, RENDERING SAID SILVER HALIDE DEVELOPERAND SAID SILVER HALIDE SOLVENT EFFECTIVE TO DEVELOP A LATEN IMAGE INSAID SILVER HALIDE LAYER AND TO FROM SOLUBLE SILVER COMPLEX WITH THEUNDEVELOPED SILVER HALIDE OF SAID SILVER HALIDE LAYER, SAID LIQUID, UPONRELEASE, ADDITIONALLY TRANSPORTING SAID SOLUBLE SILVER COMPLEX IN THEDIRECTION OF SAID SILVER PRECIPITATING AGENT WHEREIN PART AT LEAST OFTHE SOLUBLE SILVER COMPLEX IS REDUCED TO SILVER TO PRODUCE THE POSITIVEPRINT.